Rain Gauge Heater Control

The rain gauge heater is completely home-brewed and will require some ingenuity to come up with a working design. The following are more guidelines than anything else. If you come up with a solution that works well for you, share it with the group!

The heater is made up of two or more resistors in series, arranged around the tipping buckets in the rain gauge. The resistors are fed by an AC voltage source that is switched by the X1W-1. For example, one manufacturer uses two 15 ohm resistors rated at 12 watts each fed by a 24 VAC power source.

Take care when mounting the resistors. Remember, they will get hot! The mount must somehow insulate the resistors from the typical plastic body used by the gauge manufacturer. There are suitable commercial mounting kits available for wirewound power resistors. Just be sure the type you use does not conduct the heat away from the body and melt the plastic! Heat by radiation is what we want, not by conduction.

While the output of the control is open drain and can sink up to 300 mA, it is inadequate to handle the heater load. A solid state or mechanical relay must be employed to actually control the heater. Both methods are discussed below.

Solid-State Relay - This would be the preferred method as solid-state relays are very reliable. If this option is chosen, be sure you follow the assembly instructions for the Solid-State Relay Option in the appropriate section.

Mechanical Relay - This option will work, so if you already have a mechanical relay, you may wish to do this instead. As with the previous option, be sure to do follow the Mechanical Relay Option in the assembly instructions.

Refer to the schematic on how to hook up either of the above interfaces.

When assembling the connectors, wires should be crimped and soldered to the pins to insure a good electrical connection. While the pins can be inserted any number of ways into the housing, they should be oriented so that the raised tab on the pin snaps into the opening on the housing. See the illustrations.

Currently, only N4XI's WXN Server supports aspirator control. The software will automatically cycle the heater on when the falls below 34° and off when it rises above.